Disabling IPV6_V6ONLY a bad idea?

Hello,
Should I be worried about disabling IPV6_V6ONLY on a socket? The fact
that it's enabled by default made me curious enough to try some more or
less creative Google searches. Some of the results are along the line of:
- "The option was for a period of migration, which was supposed to
happen ten years ago.".
- "Disabling IPv6_V6ONLY killed my cat!" (i.e. over-the-top
non-specific security concerns).
- "It doesn't work properly on most platforms."
Outdated blogs/articles? Are there any compelling not to use
IPv4-on-IPv6, and instead bind to two separate ports?
--
Kind regards,
Jan Danielsson